A display output device which receives resolution information from an image display device, and which adjusts the resolution of a video signal which it outputs to an image display device based thereupon, has been disclosed in Japanese Laid-Open Patent Publication 2005-167895, Japanese Laid-Open Patent Publication 2004-102027, Japanese Laid-Open Patent Publication 2004-102063, Japanese Laid-Open Patent Publication 2001-111914, etc.
In Japanese Laid-Open Patent Publication 2005-167895, there is disclosed an image display device which is adapted, when an image display device and an display output device according to the HDMI standard are used, to be able to select an image format which is compatible with both of these devices, so that it is not necessary for the user to specify an image format according to which these devices can be connected together.
Here, the HDMI (High Definition Multimedia Interface) standard is a digital video and audio input and output interface standard settled upon in December 2002, and which is principally aimed at household electronics and AV devices. According to this standard, it is possible to transmit and to receive video and audio control signals together upon a single cable. And, with a device which complies with this HDMI standard, along with it being possible to transmit a video signal at 720×480 resolution, it is also possible to display an image at this resolution.
In Japanese Laid-Open Patent Publication 2004-102027, there is disclosed a structure in which, in an implementation of a multi-monitor environment with a PC, device information is transferred mutually to and fro between the image display device and the PC, in order to output an image at the optimum refresh rate. Furthermore, in Japanese Laid-Open Patent Publication 2004-102063, the concept is described of acquiring EDID (Extended Display Identification Data) information from the device on the downstream side, and of rewriting the display resolution information of the device on the upstream side.
Moreover, in Japanese Laid-Open Patent Publication 2001-111914, for a digital device which receives digital broadcasts which are broadcast in a plurality of formats and outputs a video signal to a television, in order to implement a transmitter which automatically decides whether or not some television is compatible with multiple formats, the concept is described of a structure which makes a decision upon the broadcast format from, for example, the TS (transport stream), and which controls an video signal selection means based upon the scanning frequency of the receiver, by changing over a switch so as to perform conversion, or not, based upon the value of the scanning frequency from the television which has been detected.
As described above, in the case of an image display device which complies with the HDMI standard, it must be possible to receive and to display a video signal at the resolution of 720×480. However, when a request is made by the display output device which outputs the video signal for transmission of resolution information, there are some image display devices which comply with the HDMI standard but which transmit resolution information being lack of information of 720×480. When this occurs, according to the resolution information which has been received from the image display device, the display output device may make a decision that the device cannot perform output at the resolution of 720×480. This imposes an inconvenience upon the user, which constitutes a problem. Furthermore there has been the problem that, in a case such as one in which the display output device can only perform output at the resolution of 720×480, it may not be possible to connect it with an HDMI cable but only with an analog pin cable, and product claims or customer returns are sometimes founded upon this matter.
Moreover, although in Japanese Laid-Open Patent Publication 2004-102027 the concept is described of the selection of the optimum resolution being entrusted to the user, there is the problem that, from the point of view of the user, this selection is a troublesome task. Furthermore, during this selection, there is a fear that display at a resolution of 720×480, as specified according to the standard, may not be performed, and may not be able to be selected.
Accordingly, the present invention takes it as its object to provide a display output device which is endowed with functions of receiving resolution information from an image display device which displays an image and of adjusting the resolution while outputting a video signal based thereupon, and which particularly selects the optimum resolution in a reliable manner.